Support navBarTransparent on Android

android/app/src/main/java/com/reactnativenavigation/params/StyleParams.java

     public boolean drawScreenBelowTopBar;
 
     public boolean titleBarHidden;
+    public boolean topBarTransparent;
     public Color titleBarTitleColor;
     public Color titleBarSubtitleColor;
     public Color titleBarButtonColor;

android/app/src/main/java/com/reactnativenavigation/params/parsers/StyleParamsParser.java

 
         result.topBarColor = getColor("topBarColor", getDefaultTopBarColor());
         result.titleBarHidden = getBoolean("titleBarHidden", getDefaultTopBarHidden());
+        result.topBarTransparent = getBoolean("topBarTransparent", getDefaultTopBarHidden());
         result.titleBarTitleColor = getColor("titleBarTitleColor", getDefaultTitleBarColor());
         result.titleBarSubtitleColor = getColor("titleBarSubtitleColor", getDefaultSubtitleBarColor());
         result.titleBarButtonColor = getColor("titleBarButtonColor", getTitleBarButtonColor());
 
         // TODO: Uncomment once we support drawBelowTopBar again
         //result.drawScreenBelowTopBar = params.getBoolean("drawBelowTopBar", isDefaultScreenBelowTopBar());
-        result.drawScreenBelowTopBar = true;
+        result.drawScreenBelowTopBar = !result.topBarTransparent;
 
         result.bottomTabsHidden = getBoolean("bottomTabsHidden", getDefaultBottomTabsHidden());
         result.drawScreenAboveBottomTabs = !result.bottomTabsHidden &&
     }
 
     private boolean getDefaultTopBarHidden() {
-        return AppStyle.appStyle != null && AppStyle.appStyle.titleBarHidden;
+        return AppStyle.appStyle != null && AppStyle.appStyle.topBarTransparent;
     }
 
     private StyleParams.Color getDefaultTopBarColor() {

android/app/src/main/java/com/reactnativenavigation/screens/SingleScreen.java

         if (screenParams.styleParams.drawScreenBelowTopBar) {
             params.addRule(BELOW, topBar.getId());
         }
-        addView(contentView, params);
+        addView(contentView, 0, params);
     }
 
     @Override

android/app/src/main/java/com/reactnativenavigation/views/TopBar.java

 package com.reactnativenavigation.views;
 
 import android.content.Context;
+import android.graphics.Color;
+import android.os.Build;
 import android.support.design.widget.AppBarLayout;
 import android.support.design.widget.TabLayout;
 
         if (styleParams.topBarColor.hasColor()) {
             setBackgroundColor(styleParams.topBarColor.getColor());
         }
+        if (styleParams.topBarTransparent) {
+            setTransparent();
+        }
         setVisibility(styleParams.topBarHidden ? GONE : VISIBLE);
         titleBar.setStyle(styleParams);
         setTopTabsStyle(styleParams);
     }
 
+    private void setTransparent() {
+        setBackgroundColor(Color.TRANSPARENT);
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
+            setElevation(0);
+            setOutlineProvider(null);
+        }
+    }
+
     public void setTitleBarRightButtons(String navigatorEventId, List<TitleBarButtonParams> titleBarButtons) {
         titleBar.setRightButtons(titleBarButtons, navigatorEventId);
     }

src/deprecated/platformSpecificDeprecated.android.js

   return {
     statusBarColor: originalStyleObject.statusBarColor,
     topBarColor: originalStyleObject.navBarBackgroundColor,
+    topBarTransparent: originalStyleObject.navBarTransparent,
     titleBarHidden: originalStyleObject.navBarHidden,
     titleBarTitleColor: originalStyleObject.navBarTextColor,
     titleBarSubtitleColor: originalStyleObject.navBarTextSubtitleColor,